My guess is that the TableMatrix widget keeps two copies of the text. One that reflects the applications view of that text; and one that gets manipulated for the display purposes. And what you are querying is the former rather than the latter.
That's what it looks like.

Maybe if you could work out the appropriate incantations for using the windowCget() method to obtain the text from the cells directly rather than via the TableMatrix, it might return the wrapped text.
That could work but I don't know how to figure out said incantations. I might email the TableMatrix author to see if he has some easy solution up his sleeve but the module hasn't been updated in 5 years so hopes are slim.

I also found this:It looks like that TableMatrix does not support auto-resize.
But it won't be too difficult for you to calculate the number of lines that the text of a cell occupies. To simplify the matter: 1) don't auto-resize the width (use ColWidth function to get the current width of a cell), and only auto-resize the height; 2) Measure height and width in characters, not pixels.
When you calculate the number of lines, don't forget to handle special characters like \n.
Call RowHeight to resize the cell (height only). - http://qs1969.pair.com/~perl2/index.pl?node_id=882420

The trouble is that I would need to abandon width auto-resizing (it seems that colWidth doesn't report correct values if a column is auto-resized to fit the window. On top of that, if a column is resized by dragging the border, it reports width in pixels, not characters.)

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